<!DOCTYPE html>
<html lang="zh-CN">
    <head>
        <meta charset="UTF-8" />
        <title>21_盒子模型-外边距-可以写负数</title>
        <style>
            #d1 {
                width: 200px;
                height: 200px;
                background-color: aqua;
                border: 1px solid black;
            }

            #d2 {
                width: 200px;
                height: 200px;
                background-color: rgba(255, 0, 0, .2);
                border: 1px solid black;

                margin-top: -100px;
            }
        </style>
    </head>
    <body>
        <div id="d1"></div>
        <div id="d2"></div>
    </body>
</html>